The invention relates to electrically heated couplings, in particular couplings for cabling used in a vehicle.
A vehicle contains various types of containers or tanks containing liquids used for different purposes in the vehicle. There is often a need for maintaining such fluids above a certain temperature to ensure that the equipment using the fluid may be operated as intended. In some cases it is sufficient to add an anti-freeze to the liquid to prevent the liquid from freezing. In other cases the use of anti-freeze is not possible, as this can affect the functional properties of the liquid. In the latter cases the container or tank can be provided with a suitable heating device for melting the liquid if it freezes. The heating device can be activated before or during starting of the vehicle, depending on the ambient temperature and the volume of liquid to be melted. To ensure proper function of a system containing the liquid, hoses or cabling conveying the liquid to or from the tank must also be defrosted. This requires additional heating devices for melting any frozen liquid in the hose.
The present invention can be used in connection with heating of different types of hoses and cabling and is not limited for use in vehicles. In the subsequent text the invention will be described in connection with a particular implementation, namely heating of hoses used for conveying liquid urea, commercially available as AdBlue®. This liquid is a non-toxic aqueous urea solution used to chemically reduce nitrogen oxide (NOx) emissions, in particular for heavy-duty diesel powered vehicles. However, the invention is not limited to the heating of hoses for this purpose.
For commercial vehicles, cold starts should be possible in temperatures down to −400 C. Consequently it is also required that the exhaust purification system should perform satisfactorily at such temperatures. As urea is an aqueous solution that can not be mixed with, for instance, an alcohol based anti-freeze, there is a need for heating hoses conveying urea.
There are various ways of heating the fluid in a hose. One way is to heat the hose with the cooling water. This means that the heating is delayed until the engine has warmed up and that a number of extra hoses and connections are required for conveying water to multiple locations around the vehicle. This solution is both expensive and unnecessarily complicated.
A simpler way is to heat the hose using electricity. Hoses can be provided with electrical wiring comprising one or more wires that may be wound spirally around the inner conduit inside the material making up the hose. The electrical wiring may be incorporated between individual layers in the hose or be an integral part of the body of the hose. A problem with such known solutions is that heating is only provided for the hose itself.
In addition, there are particular types of commercial vehicles intended for the transportation of dangerous goods, for which special safety requirements apply. There are both national safety requirements, drawn up by many individual countries, as well as international agreements that regulate safety requirements at an international level. One such international agreement is “The European Agreement concerning the International Carriage of Dangerous Goods by Road”, commonly referred to as ADR, first agreed in Geneva on the 30th of September 1957 under the auspices of UNECE. This agreement has since been updated.
The agreement regulates how dangerous goods are to be transported in goods vehicles by road. One of the requirements is that it must be possible to cut off the supply voltage of the vehicle while in motion. For example, when the ADR system detects a safety-related occurrence or in the event of an accident, the driver activates an emergency cut-off switch in the cab. In addition, the electrical cabling must be encapsulated. For certain vehicles, there are also requirements that the electrical cabling must fulfil the protection classification IP69K for wash down protection. One of the requirements for this protection classification is that all electrical cabling must be completely encapsulated. This encapsulation can be carried out using, for example, corrugated plastic hose.
Vehicles that are to be ADR-classified must usually be specially ordered with special equipment that ensures that the vehicle meets the requirements laid down. In order not to need to have to redesign the whole vehicle when an ADR-classified vehicle is to be manufactured, it is advantageous for as much as possible of the vehicle's standard equipment to meet the requirements of the ADR classification. This reduces the number of components, which simplifies the production. As an ADR-classified component is often more robust than a standard component, this is also advantageous for the quality of the vehicle.
Providing an ADR-classified vehicle with a fluid hose that is heated electrically is a difficult problem. As the fluid hose is required to be able to be connected and disconnected, releasable connectors must be provided for both the hose connectors and the electrical connectors. At the same time, all electrical cabling must be encapsulated so that all parts of the cable are protected.
There are several known arrangements for heating a hose for fluids. WO 2002/38426, EP 0 045 024 and DE 297 15 336 describe systems where a heating cable is located in the fluid conduit of the hose. A disadvantage is that such a solution can cause leakage at the connection points where the cable enters the hose. In addition, it is not desirable to immerse an electrical cable in urea or in fluids with corrosive properties.
U.S. Pat. No. 5,791,377, EP 0 616 166, EP 1 040 973 and DE 198 44 486 describe fluid hoses where the heating cable is integrated in the wall surrounding the fluid conduit of the hose. In these examples, the electrical leads are provided with some form of special electrical connector for connecting the electrical current, with the electrical connector also being attached to the hose itself. The disadvantage of these solutions is that they require an extra electrical connector. This is an expensive solution which is not particularly robust, as a relatively large electrical connector attached to a narrow hose is a mechanically unsatisfactory solution.
DE 3 900 821, EP 1 329 660, DE 198 44 485, DE 3 900 821 describe additional fluid hoses in which the heating cable is integrated in the wall of the hose. The connection of the heating cable can be carried out in a conventional way, which means that the heating cable is unprotected where it comes out of the hose. This solution is not suitable for use in a vehicle.
A common problem for the above prior art documents is that they only provide means for heating the hose itself. The connectors used for connecting the hose to a tank or to the equipment to be supplied with fluid may in some cases be protected from humidity and/or external forces, but are otherwise exposed to the surrounding environment.
It is therefore desirable to provide a connector for a fluid hose that is protected from humidity and external forces, as well as being provided with means for allowing operation in sub-zero ambient temperatures.
According to a preferred embodiment, the invention relates to a cabling for a motor vehicle, which cabling may comprise at least one fluid hose, a first cable for heating the fluid hose and at least one electrical connector for connecting the cable to an electrical supply. The cabling further comprises at least one hose connector for connecting the fluid hose to a cooperating connector means. In order to defrost or heat the hose connector it is provided with an electrically heated device that may be arranged to heat at least part of the hose connector. The heated device may be dimensioned to thaw a frozen hose connector in about one hour from −400 C or about half an hour from −20° C. The heated device may also be required to maintain the hose connector above a predetermined temperature during operation of a vehicle. Some form of temperature control may be required for this purpose. Various suitable heating devices are described below.
According to one embodiment the first electric cable used for heating the fluid hose is used to supply electric power to the electrically heated device. In this case, the first cable is preferably, but not necessarily, integrated in the fluid hose. The first cable may be connected to the electric supply at one end and may be provided with electrical connectors or electrical splicing devices for the electrically heated device at a second end.
The electrically heated device may be connected in parallel to the first cable for heating the fluid hose. This alternative may be used for an electrically heated device of the positive temperature coefficient (PTC) type or an electrical resistance device. A positive temperature coefficient or PTC device may also be referred to as a PTC heater or PTC resistor and is a ceramic element whose zero-power resistance increases with an increase in temperature. In the subsequent text the term “PTC device” will be used. When a PTC device is heated above a predetermined temperature by a voltage applied across it, the PTC device will auto-stabilize at a fixed temperature. If its temperature should decrease, the resistance will drop and more current is drawn to counter the cooling effect. The opposite effect occurs if the temperature increases. In addition, the performance of the PTC device is nearly independent of voltage over a relatively wide voltage range. The above features are particularly well suited for the purpose of thawing or heating a hose connector, as a predetermined temperature can be obtained even if the available supply voltage from, for instance, the vehicle batteries should vary.
Alternatively, the electrically heated device may be connected in series with the first cable for heating the fluid hose. This alternative may be used for an electric resistance heater or for an electrically heated device of the negative temperature coefficient (NTC) type. A negative temperature coefficient or NTC device may also be referred to as a NTC heater or NTC resistor and is a device whose zero-power resistance decreases with an increase in temperature. In the subsequent text the term “NTC device” will be used. The NTC device may be used alone or in combination with an electric resistance heater. When used in combination with an electric resistance heater, the NTC device may be a resistor that will experience a drop in resistance with an increase in temperature and may be embedded in the electrically heated device to control temperature. This NTC resistor may be wired to a switch, inside which is a relay that switches off the current to the electric resistance heater as a selected temperature is reached.
In the above examples, where the first cable is used for supplying electric power to the electrically heated device, the fluid hose and the first cable may be surrounded by a first external protective sheath. If the cabling arrangement is used for a vehicle of the ADR type, a typical external protective sheath may be a corrugated plastic tube of the type Polyflex® manufactured by Schlemmer Cable Protecting Systems. The choice of corrugated tube from the Polyflex®-series may vary depending on the type of use and what temperatures and/or chemical substances the tube may come into contact with. The corrugated plastic tube may preferably extend over the entire length of the fluid hose and is provided with end seals at both ends. The end seal may be an annular, relatively hard but flexible, rubber, polymer or metal washer fitted over, snapped onto or integrated with the hose connector. The corrugated plastic tube may be attached to or snapped onto said annular washer. Preferably, however, an intermediate manifold may be provided between the end seal and the corrugated plastic tube. In order to protect any electric cables supplying electric power to the fluid hose and the at least one electrically heated device for one or more hose connectors, a manifold may be provided for at least one end of the fluid hose. A typical manifold for this purpose may be a Y-manifold with a snap-lock as manufactured by Schlemmer Cable Protecting Systems®. In this case, the manifold is snapped onto said annular washer at one end and snapped over the corrugated plastic tube at its other end. The cable exiting such a manifold for connection with the electrical supply may be surrounded by an external protective sheath in the form of a corrugated plastic tube of the same type as used for the fluid hose. Adjacent an end seal where no electrical cables are introduced, a straight, tubular manifold, or 1-manifold, may be used.
According a further embodiment the first cable is used for heating the fluid hose and a second electric cable is used to supply electric power to the electrically heated device. This second cable may be integrated in the fluid hose, together with the first cable, or be arranged parallel to the fluid hose. In this case, the fluid hose, the first cable and the second cable may be surrounded by a first external protective sheath as described above. The first and second cables may be connected to the electrical supply from the end of the fluid hose remote from the hose connector to be heated.
Alternatively, either a single second cable or the first cable and the second cable are attached to the fluid hose adjacent the hose connector to be heated. The second cable may be connected to the electric supply at one end and may be provided with electrical connectors for the electrically heated device at a second end. In this case the fluid hose is surrounded by a first external protective sheath and the first cable and the second cable are surrounded by a second external protective sheath. The first and second protective sheaths may comprise corrugated plastic tubes, which are connected adjacent the hose connector by means of a manifold, as described above.
The fluid hose may also be provided with electrically heated hose connectors at both ends. In this case an electrical heating device is provided for each hose connector. The heating device may be supplied with electric power from the first cable at both ends, from the first cable at one end and the second cable at the opposite end, from a single second cable connected adjacent one end, or from a pair of separate second cables connected to each end.
In the above examples, where at least one second cable is used for supplying electric power to the electrically heated device, the heating device is preferably a positive temperature coefficient, or PTC device. However, the heating device may also be a negative temperature coefficient, or NTC device and/or an electric resistance heater. Such heaters have been described above.
According to a preferred embodiment, the heating device may be attached to the hose connector by a clip-on device. The heating device is preferably, but not necessarily, integrated in a clip-on device attached to the hose connector. In order to protect the hose connector from ambient cold air, when the vehicle is stationary, and/or cold air is flowing past the connector, during windy conditions or when the vehicle is moving, the clip-on device is arranged to surround the hose connector on at least three sides. The clip-on device may be attached by snapping it directly onto the hose connector, onto the end seal for the corrugated plastic tube enclosing the fluid hose or onto both the hose connector and the end seal.
A clip-on device surrounding the hose connector on three or four sides may comprise a single, one-piece unit. The heating device may be attached onto one or more inner surfaces of the unit, or be integrated in the unit be, for instance, moulding. A clip-on device surrounding the hose connector on all sides may comprise two attached or separate, substantially identical halves that may be snapped on and/or screwed together. Two attached or separate and asymmetric parts may also be used. The attachment between two parts may comprise one or more flexible hinges that allow the two parts to be folded around the hose connector and be snapped and/or screwed together.
The clip-on device may also be provided with a surrounding insulating layer covering selected parts of or the entire outer surface of the device. In order to ensure insulation between a pair of mating hose connectors, the insulating layer on each facing clip-on device may be elastic and extend a short distance beyond each end surface of the respective facing clip-on devices. When the hose connectors are joined, the end of the insulating layer of each facing clip-on device will be compressed and seal any gap between the clip-on devices.
The hose connector may be formed as a substantially straight component, where the fluid conduit is arranged along an axis through the centre of the connector. Alternatively, the hose connector may be formed as an angled component. In the latter case, the section of the hose connector facing away from the fluid hose may have a fluid conduit located at an angle up to and including 90° relative to the fluid conduit extending into the fluid hose. In order to attach the clip-on device directly onto either a straight or an angled hose connector, the clip-on device may have an open U-shaped cross-section and a length substantially equal to the extension of the hose connector from the outer surface of the end seal. The width of the U-shaped cross-section may be selected to allow the clip-on device to be fitted over and in relatively close proximity to the hose connector.
The inner geometry of a clip-on device may be adapted in order to allow a single clip-on device to be used for at least two types or sizes hose connectors. For instance, if the cabling is to be used for hoses using angled hose connectors having two different angles, it is desirable to provide a clip-on device that may be fitted over hose connectors irrespective of its angle.
The clip-on device and the hose connector and/or the end seal may be provided with co-operating grooves and protrusions. If a standard hose connector is used, then the clip-on device can be arranged to be snapped onto the body of the hose connector, or to co-operate with any available circumferential grooves or protrusions. A common end seal comprises a circular disc clamped in an axial position between the hose connector and the fluid hose. Such an end seal may be provided with a circumferential groove that can be used for snapping on the clip-on device. Alternatively, the end seal may be provided with an outer circumferential profile specially adapted for co-operation with a similarly shaped clip-on device. In this way, the clip-on device may be snapped onto the hose connector and/or the end seal in a direction substantially at right angles to the axis of the fluid conduit extending into the fluid hose. A manifold may be snapped directly onto the end seal or over the clip-on device.
According to a further alternative, the end seal may be integrated with an end of the clip-on device. In this way, the clip-on device may be snapped onto the hose connector and/or the end seal in a direction substantially at right angles to the axis of the fluid conduit extending into the fluid hose. A manifold may then be snapped directly onto the clip-on device.
Clip-on devices as described above may enclose the hose connector on at least three sides, wherein an electrical heating device may be provided in at least one of the three sides. In order to connect the electrical heating device to the first or the second cable, a recess may be provided through the end seal at a suitable location to allow sufficient space for at least a pair of electrical leads.
A hose connector formed as an angled component may be provided with an alternative clip-on device. Such a clip-on device may comprise a profile with a U-shaped cross-section having a closed surface at one end and a length substantially equal to the extension of the hose connector from the outer surface of the end seal. The clip-on device and the hose connector and/or the end seal may be provided with co-operating grooves and/or protrusions. Depending on the location of the co-operating grooves and protrusions, the clip-on device may be snapped onto the hose connector and/or the end seal. By selecting the locations of the co-operating grooves and/or protrusions on the clip-on device, the device may be snapped on either in a direction substantially at right angles to the axis of the fluid conduit extending into the fluid hose, or in a direction substantially parallel to the axis of said fluid conduit. Such a clip-on device will enclose the angled hose connector on four sides, wherein an electrical heating device may be provided in at least one of the four sides. As described above, a recess may be provided through the end seal at a suitable location to allow sufficient space for at least a pair of electrical leads.
For a manifold, formed as a substantially straight component, an additional clip-on profile, having a similar U-shaped, or flat cross-section and a corresponding length may be provided. By clipping this additional profile onto the U-shaped profile as described above, the hose connector may be protected on four sides. Alternatively, a split component having two halves joined by an integrated hinge could be provided, wherein one or both halves could be provided with heating devices.
For both types manifold an alternative solution may be to integrate the end seal in the clip-on device. In order to provide a seal around entire circumference between the end seal and the manifold, a split, two part clip-on device is preferred. Suitable arrangements for split or two piece clip-on devices for surrounding the hose connector on all sides has been described above.
As an alternative to the clip-on device, the heating device may be integrated in the hose connector. This is a more expensive arrangement, as a standard hose connector can not be used. On the other hand, the through-connection of the electric cable may not require a recess through the end seal, as described above. Instead the end seal can be integrated in the hose connector, whereby a pair of electrical leads or a plug-in socket can be provided in the end surface facing the fluid hose. This solution may also require additional protection and/insulation during cold weather conditions.
As stated above, it is desirable to provide an electrically heated fluid hose with at least one hose connector having an electrically heated device that may be arranged to heat at least part of the hose connector. A common feature for all embodiments is that the heated device should be located in close proximity to, or even in contact with, the hose connector to be thawed and/or heated. The fluid hose and the electrical cable for heating the fluid hose and said at least one hose connector are preferably protected from the surrounding environment. It is also desirable to fulfil various safety requirements, such as the ADR requirements, that require all electrical cables to be completely protected, in a simple way and without expensive special components.
An advantage of providing the fluid hose with hose connectors is that the cabling can be connected to and disconnected from a fluid system in a simple way. The protective sheath comprises at least one corrugated plastic tube and at least one connector or end seal. The advantage of this is that the protective sheath can be constructed from inexpensive standard components. The advantage of arranging the said hose connector and said electrical connector separate from each other is that inexpensive standard electrical connectors and standard hose connectors can be used.